REVIEW are the most important biomass producers in global




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            Phytoplanktons are the most
important biomass producers in global aquatic ecosystems.  The organisms populate the top layers of the
oceans and freshwater habitats where they receive sufficient solar radiation
for photosynthesis (Hader et al., 1998). 
Algae produce approximately 52,000,000,000tons of organic carbon per
year, which is almost 50% of the total organic carbon produced on earth each
year (Field et al., 1998).  Therefore it
appears to be an important biomass producer using atmospheric carbon dioxide
and solar energy.  Hence there is an
increasing quest all over the world to explore microalgae to address various
applications in pharmaceutical, nutraceutical and food, textile, aquaculture,
biofuel, and carbon dioxide mitigation, bioremediation of heavy metals and for
many such prospective industrial and commercial applications.

            Algae are the simple photosynthetic
aquatic organisms belong to both eukaryote and prokaryota (Gupta, 1981).  They exist as single -celled organisms to
multicellular organisms with fairly complex differentiated from than the single
celled ones.  These complex forms are
distinguished as macroalgae which includes the marine forms such as
seaweeds.  They are devoid of well differentiated
structures such as leaves, roots, flowers, and other organ structures that
characterize higher plants(Dawson, 1966; Fritsch, 1977).

            The history of algae is as old as
human civilization, people collected macro algae and seaweeds for food around
2,500 years ago in china (Tseng, 1981). 
The use of microalgae by humans dates back 2000 yas to the Chinese, who
used Nostoc to survive during famine (Spolaore et al., 2006).  Japanese also found macroalgae as a food
source during the 4th centure (McHugh, 2003).  Europeans started using seaweeds in their
diet from the past 500 years (Mccoy,1987). 
During the mid -17th century Japanese have started
cultivating seaweeds for food supplement(Pulz and Gross 2004).  Nostoc, Spirulina, and Aphanizomenon species
have been exploited for many centuries in Asia, Africa and Mexico as a
nutrient-dense food )Jensen et al.,2001; Olaizola 2003).  In the 1940s, microalgae become popular as
live feeds in aquaculture.  After 1950s,
algal biotechnology developed rapidly, starting in Germany and extending into
the USA, Israel, Japan, and Italy for producing protiein and fat as a nutrition
source from algal biomass (Burlew,1953). 
Simultaneously the use of microalgae in wastewater treatment and the
synstematic examination of algae for biologically active substances,
particularly for antibiotics was also initiated(Borowitzka, 1995).  During 1960s, the commercial production of
Chlorella as a novel health food supplement was a big success in Japan and
Taiwan (Kawaguchi, 1980).  In USA,
interest grew in developing algae as photosynthetic gas exchangers for long
term space travel as well (Borowitzka, 1999). 
Energy crises during 1970s energized the idea of using microalgal
biomass as renewable fuels and fertilizers with an eco-friendly process (Pulz
and Scheibenbogen, 1998; Spolaor et al., 2006). 
At the same time first large scale spirulina production plant was
established in mexico(Borowitzka, 1999) and later during 1980s and onwards
there were more than 46 large-scale algae production plants in Asia
particularly in india, and large commercial production facilities in the USA
and Israel wre started to operate for microalgae production for protein, fat
and for other nutraceutical and pharmaceutical molecules (Spolaore et al., 2006).

            Particularly during the last two to
three decades, algal biotechnology grew progressively and occupied a key
position in scientific world to address various aspects of environment and
mankind.  Scientific and technological
information on algae is accumulating day by day and thus various algologists,
ecologists, environmentalists, policy makers and industrialists look forward to
explore these tiny wonderful plants for diversified applications in
agricultural, food, medicine and for environmental prospective.  This radical shift in phycological research
has initiated various groups of researchers across the globe to explore the
potentials of algae to address various environmental, food and biofuel
issues.  Currently almost all countries
across the continents are using microalgae for various food, health and other
benefits.  Today, more than 40,000 algal
species are known (Hallmann, 2007).